As batteries are more and more widely used nowadays, demand for enhanced battery performance is growing. High power outputs are required for many equipments, such as an electric vehicle, etc. Conventionally, a plurality of single cells are connected to form a power battery pack. These single cells include positive electrode poles and negative electrode poles connected in parallel and/or in series to form a desired power source with a high power output. However, the connections may cause a high contact resistance, heavy weight, unstable connection, weak sealing problems, etc., which may affect battery safety and output performance.